<head>
<style>
a { color: green; }
</style>
</head>
<body>
<script>
function toggle(id)
{
    var node = document.getElementById(id);
    node.style.display == 'none' ? node.style.display = 'block' : node.style.display = 'none';
}
</script>

<div style="border:2px solid red"><a onclick="toggle('first');">First</a><span id="first" style="display:none"> 
&nbsp;First Content.
</span><a onclick="toggle('second');">Second</a><span id="second" style="display:none">
&nbsp;Second Content.
</span><a onclick="toggle('third');">Third</a><span id="third" style="display:none">
&nbsp;Third Content.<a onclick="toggle('crashme');">&nbsp;Crash Me</a><span id="crashme" style="display:none">
&nbsp;&nbsp;You win!
</span></div>